Earth's stratosphere is normally free of clouds. Not this weekend, though. Observers around the Arctic Circle are reporting an outbreak of brilliantly-colored icy clouds in the typically dry and transparent layer of our planet's atmosphere. Eric Fokke photographed the display on New Years Eve from the Lofoten Islands of Norway:

These icy clouds are a sign of very cold temperatures. For ice crystals to form in the arid stratosphere, temperatures must drop to around -85º C. High-altitude sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors.Once thought to be mere curiosities, some polar stratospheric clouds (PSCs) are now known to be associated with the destruction of ozone. Indeed, an ozone hole formed over the UK in Feb. 2016 following an outbreak of ozone-destroying Type 1 PSCs.

These clouds really are as amazing as they look in Fokke's photo. They have much more vivid colors than ordinary iridescent clouds, which form closer to Earth in the troposphere. Once seen, a stratospheric cloud is never forgotten.www.spaceweather.com

Sept. 20, 2016: Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:

This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.

What is this all about? Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly space weather balloons to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 12% since 2015:

Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.

The data points in the graph above correspond to the peak of the Reneger-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Reneger and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.www.spaceweather.com

The stratosphere is a relatively clear layer of Earth's atmosphere, almost always cloud-free. Almost always. On Monday, researchers at Argentina's San Martín Base spotted a bank of fantastically colored clouds floating in the stratosphere above the Antarctic Peninsula:

"There were the biggest stratospheric clouds we've seen so far this year," says photographer "Marcelo," who is working at the Base this winter. "It was a colorful spectacle to begin the day."These are called "Polar Stratospheric Clouds" (PSCs). They form in the lower stratosphere when temperatures drop to around minus 85º C. This explains why they are rare; even at the poles, such low temperatures are hard to achieve. High-altitude sunlight shining through tiny (~10µm) ice particles in PSCs produce bright iridescent colors by diffraction and interference. Once thought to be mere curiosities, some PSCs are now known to be associated with the destruction of ozone. www.spaceweather.com

An outbreak of polar stratospheric clouds (PMCs) is underway around the Arctic Circle. Unlike normal grey-white clouds, which hug Earth's surface at altitudes of only 5 to 10 km, PMCs float through the stratosphere (25 km) and they are fantastically colorful. Sarah Skinner saw this specimen high above Abisko, Sweden:

"Just as I was heading out to de-ice the car on Dec. 14th, I looked up and noticed the most incredible cloud formation," says Skinner. "At the same time, an excited text came through from my boss, aurora tour guide Chad Blakley, who having lived here for many years has seen this only once or twice and explained to an Arctic newbie like me how rare these formations really are."Also known as "nacreous" or "mother of pearl" clouds, the icy structures form in the lower stratosphere when temperatures drop to around minus 85ºC. Sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors by diffraction and interference. Once thought to be mere curiosities, some PMCs are now known to be associated with the destruction of ozone.

"Nacreous clouds far outshine and have much more vivid colours than ordinary iridescent clouds, which are very much poor relations and seen frequently all over the world," writes atmospheric optics expert Les Cowley. "Once seen they are never forgotten." www.spaceweather.com

Published on 23 Mar 2015
Timelapse movie of the moon shadow seen from the stratosphere, in a plane flying along the umbral path of the sun eclipse of 20th March 2015.

CHASING MOON SHADOWS: Total eclipses of the sun are achingly brief. The Moon's shadow races across the landscape at thousands of kilometers per hour, enveloping sky watchers for a matter of minutes at most. On March 20th, when the Moon passed in front of the sun over the Arctic Ocean, a few observers extended the experience--in an airplane. "Flying at 14,000 m was an incredible way to watch the eclipse," reports Sylvain Chapeland. "Our velocity of 950 km/h allowed an extra minute of totality." She recorded this must-see video over a stretch of ocean between Iceland and the Faroe Islands:

"I have never seen anything like the shadow of the Moon rushing upon us during totality, overtaking us and continuing its path at 3000 km/h," says Chapeland. "This was a dramatic perspective. Our view of the sun's corona with Venus shining on the east side were incredible."

Lunar eclipses are supposed to be red, yet when the Moon passed through Earth's amber shadow on April 15th, many observers witnessed a softly-glowing band of turquoise blue. Robert and Elisabeth Slobins send this picture of the phenomenon from Fort Myers, Florida:

The source of the turquoise is ozone. Prof. Richard Keen, an atmospheric scientist from the University of Colorado explains: "During a lunar eclipse, most of the light illuminating the Moon passes through the stratosphere, and is reddened by scattering. However, light passing through the upper stratosphere penetrates the ozone layer, which absorbs red light and actually makes the passing light ray bluer!" This can be seen, he says, as a turquoise fringe around the red. For years, Keen has been using lunar eclipses to probe the transparency of the stratosphere. When the stratosphere is clogged with volcanic ash and other aerosols, lunar eclipses tend to be dark red. The bright orange color of the April 15th eclipse, along with the ready visibility of the turquoise fringe, suggests that the stratosphere is clear. This is a key finding for climate change models. To see the effects of ozone on the eclipse, you have to be looking at just the right moment. Readers are invited to browse the gallery for more examples: Realtime Eclipse Photo Gallery. www.spaceweather.com

On Oct. 27th, when the students of Earth to Sky Calculus launched a pair of radiation sensors to the stratosphere onboard a helium balloon, they didn't know what to expect. This just in: They have re-discovered the Pfotzer Maximum. Most people have never heard of it. The Pfotzer Maximum is a layer of peak radiation about 20 km above Earth's surface. Take a look at this data plot from the team's space weather balloon and keep reading below for more information:

The plot shows a complete profile of ionizing radiation between 2.7 km and 27 km above Earth's surface. Data from their sensor counted X-rays and gamma-rays in the energy range 10.0 KeV to 20.0 MeV. A peak in radiation levels occured in the tropopause--that's the Pfotzer Maximum. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles. With increasing depth in the atmosphere, the primary cosmic radiation component decreases, whereas the secondary radiation component increases. This complex situation results in a maximum of the dose rate at an altitude of ~20 km, the so-called "Pfotzer maximum," named after physicist George Pfotzer who discovered the peak using balloons and Geiger tubes in the 1930s. The Earth to Sky experiment was prompted by a recent NASA report concerning the effects of space weather on aviation. Like astronauts, ordinary air travelers can be exposed to significant doses of radiation when the sun is active. Data collected by balloon-borne sensors can be used to check and improve research models of radiation percolating through Earth's atmosphere. The students are ready to fly their sensors again. A radiation storm in the week ahead is a possibility as solar activity remains high. If one erupts, they plan to revisit the Pfotzer Maximum to find out how it reacts. Stay tuned. www.spaceweather.com

Members of the Earth to Sky Calculus science club have recovered the space weather balloon they launched on Oct. 27th. The payload, which landed in a remote area of California's Inyo Mountains, carried two high-energy radiation sensors into the stratosphere. These pictures show the erupting balloon and one of the sensors at the apex of the flight, 27 km (90,500 feet) above Earth's surface:

The reading on the LCD screen shows a dose rate of 3.7 uSv/hour, more than 20 times higher than radiation levels at the launch site. Another independent sensor was contained inside a thermally insulated capsule. Working together, the two sensors measured a complete profile of ionizing radiation from 2.8 km to 27 km above Earth's surface. This experiment was prompted by a recent NASA report concerning the effects of space weather on aviation. Like astronauts, ordinary air travelers can be exposed to significant doses of radiation when the sun is active. The Oct. 27th flight showed that it is possible to count x-rays, gamma-rays, alpha particles and beta particles using relatively inexpensive equipment. Such data can be used to check and improve research models of radiation percolating through Earth's atmosphere. Another balloon flight could be in the offing. Solar activity is high, and a new fusillade of X-flares could trigger a radiation storm around Earth. If so, the student scientists plan to send their sensors back to the stratosphere for another look. www.spaceweather.com

On July 24th, about an hour after sunset, Gerardo Connon of Rio Grande city in Tierra del Fuego, Argentina, walked outside and witnessed a rare display of nacreous clouds. The colorful apparition was as bright as the street lights in the city below:

These clouds, also known as "mother of pearl clouds," form in the stratosphere far above the usual realm of weather. They are seldom seen, but when they are, the reports usually come from high-northern parts of our planet. This apparition over Tierra del Fuego was unusual indeed. Atmospheric optics expert Les Cowley explains the special conditions required to create such a cloud: "Take an unusually cold lower stratosphere (15-25km high), use some gravity waves generated by high winds and storms in the troposphere to stir in some water vapour, and -- voilà! You get these clouds made of tiny ice crystals shining after sunset with unforgettably bright iridescent colors." "The very special conditions make nacreous clouds a rare, high-latitude phenomenon. Scandinavia, Iceland and northern Canada are favourite places to see them. Sightings in the southern hemisphere are even more rare because there is so little land far enough south except for Antarctica." www.spaceweather.com

To fund space weather experiments in the stratosphere, science students in Bishop, California, have started a new business: Edge of Space Advertising. For a fee, they'll fly ad banners, shoes, US presidents--you name it!--to the edge of space. On April 22nd (Earth Day), they launched a cow:

This is EVA, the mascot of New Zealand Internet service provider EOL. Last month, she traveled from Tauranga, New Zealand, to an Edge-of-Space Port in the Sierra Nevada mountains of California. There, students attached EVA to the payload of a helium balloon and launched her to the stratosphere 120,000 feet above Earth's surface. Along the way she experienced temperatures as low as -65o C and air pressures only 1% of sea level--much like conditions on the planet Mars. At the end of the 3-hour flight, the balloon popped and EVA parachuted back to Earth, touching down in a remote corner of Death Valley. GPS signals led the students to the landing site, where they recovered EVA covered with desert dust but still smiling. The name of the student group is "Earth to Sky Calculus." Mentored by Dr. Tony Phillips of spaceweather.com, they are actively exploring the stratosphere--measuring the effect of solar flares on the ozone layer, capturing high-altitude bacteria, and photographing meteor showers. The profits are going to a good cause. EVA's flight to the stratosphere and the student's recovery expedition through Death Valley has generated a flurry of news coverage for EOL in New Zealand. In short, Edge of Space Advertising really works. Interested? Contact Dr. Tony Phillips for rates and details. www.spaceweather.com

LYRID METEOR SHOWER PEAKS TONIGHT: Earth is passing through a stream of debris from ancient Comet Thatcher, source of the annual Lyrid Meteor Shower. Usually the shower is mild (10-20 meteors per hour) but unmapped filaments of dust in the comet's tail sometimes trigger outbursts ten times stronger. Forecasters say the best time to look is during the dark hours before local dawn on Monday, April 22nd. [photo gallery]

BIG SUNSPOT BOOSTS ODDS FOR FLARES: The rapid growth of sunspot AR1726 continues. Invisible only two days ago, it is now a behemoth more than 150,000 km (a dozen Earth diameters) wide.

The sunspot has a 'beta-gamma' magnetic field that harbors energy for M-class flares. NOAA forecasters put the odds of an M-class eruption today at 10%, but that is probably an underestimate. AR1726 poses a growing threat for significant Earth-directed flares. SPACE WEATHER BALLOON: Yesterday in the Sierra Nevada mountains near Bishop, California, a group of high school students launched a "space weather balloon" into the stratosphere. Their goal is to monitor the effects of solar flares on Earth's atmosphere. Scroll below the image for more information:

The silver capsule, built by Mihai Ciustea of Sammamish WA and launched by the Earth to Sky team of Bishop CA, is bristling with sensors to measure, e.g., ozone, pressure, humidity, acceleration and other variables of interest. The capsule travels to 125,000 feet--well inside Earth's ozone layer--and lingers there for approximately two hours before parachuting back to Earth with the data. The April 20th launch was a test flight to measure baseline levels when solar activity is relatively low. The capsule also serves another purpose: It is a bacteria collector. A door at the bottom of the capsule can open, guiding air into a filter designed to capture microbes during the flight. Mihai Ciustea hopes to find ice-nucleating bacteria and other lifeforms living high above Earth's surface. Stay tuned for updates about this mission! www.spaceweather.com

January 23, 2013 – CLIMATE – An unusual event playing out high in the atmosphere above the Arctic Circle is setting the stage for what could be weeks upon weeks of frigid cold across wide swaths of the U.S., having already helped to bring cold and snowy weather to parts of Europe. Forecast high temperatures on Monday, Jan. 21, from the GFS computer model.

This phenomenon, known as a “sudden stratospheric warming event,” started on Jan. 6, but is something that is just beginning to have an effect on weather patterns across North America and Europe.

While the physics behind sudden stratospheric warming events are complicated, their implications are not: such events are often harbingers of colder weather in North America and Eurasia. The ongoing event favors colder and possibly stormier weather for as long as four to eight weeks after the event, meaning that after a mild start to the winter, the rest of this month and February could bring the coldest weather of the winter season to parts of the U.S., along with a heightened chance of snow.

Sudden stratospheric warming events take place in about half of all Northern Hemisphere winters, and they have been occurring with increasing frequency during the past decade, possibly related to the loss of Arctic sea ice due to global warming. Arctic sea ice declined to its smallest extent on record in September 2012. These events occur when large atmospheric waves, known as Rossby waves, extend beyond the troposphere where most weather occurs, and into the stratosphere. This vertical transport of energy can set a complex process into motion that leads to the breakdown of the high altitude cold low pressure area that typically spins above the North Pole during the winter, which is known as the polar vortex.

The polar vortex plays a major role in determining how much Arctic air spills southward toward the mid-latitudes. When there is a strong polar vortex, cold air tends to stay bottled up in the Arctic. However, when the vortex weakens or is disrupted, like a spinning top that suddenly starts wobbling, it can cause polar air masses to surge south, while the Arctic experiences milder-than-average temperatures. During the ongoing stratospheric warming event, the polar vortex split in two, allowing polar air to spill out from the Arctic, as if a refrigerator door were suddenly opened.

For reasons I don’t think we fully understand, the changes in the circulation that happen in the stratosphere can descend down all the way to the Earth’s surface,” said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research (AER) in Massachusetts. As the polar stratosphere warms, high pressure builds over the Arctic, causing the polar jet stream to weaken. At the same time, the mid-latitude jet stream strengthens, while also becoming wavier, with deeper troughs and ridges corresponding to more intense storms and high pressure areas. In fact, sudden stratospheric warming events even make so-called “blocked” weather patterns more likely to occur, which tilts the odds in favor of the development of winter storms in the U.S. and Europe. –Climate Central

The incredible night photos and time-lapse movies NASA has been sharing with us provoke questions about our planet. That thin-yellow atmospheric line separating earth from space, for example, that we see in all of the night shots provokes two questions: (1) how thick is this line? and (2) why is this line colored the way it is?

The visible yellow and green/blue capped line represents atmosphere reaching ~100km above the surface of the earth. The colors are not reflected light, and not pollution, but rather are light generated from the components in the atmosphere itself. Yes, the atmosphere gives off its own light, in a chemiluminescent process called "airglow" or "night glow."

I have written a blog to accompany this video that explains the various colors of "Night Glow" and discusses the Aurora as well. I hope you find this blog a useful companion to understanding what you are seeing.

These images were imported into Adobe Lightroom, cropped, rotated, and slightly tweaked. I had two main goals with the edits done in the manner I did them. My first goal was to bring the viewer's attention to the atmospheric line by focusing the cropping to prominently feature the atmospheric line and the "Airglow." Secondly, most of the images we see of earth show the planet at the bottom of the frame and space at the top of the frame. To remind the viewer that, in space, the orientation by which you choose to view planets is up to the viewer, I took artistic license with these images to present different ways to view our planet's movement in space.

When the sun set over the UK on Dec. 9th, sky watchers were stunned by an unexpected apparition of super-colorful stratospheric clouds. "They were amazing to see and a dream come true to photograph," reports Lesley Jennings of Fraserburgh, Aberdeenshire, Scotland. "There were all sorts of colors. I've never see the like before!" added Rachael Taylor also from Aberdeenshire. Nigel Feilden photographed this specimen from Inverurie, Scotland:

"These are nacreous clouds," explains atmospheric optics expert Les Cowley. "Of all Earth's clouds they are most spectacular, and a very rare treat for skywatchers." "For up to an hour after sunset or before dawn they glow like eerie electric discharges or gas jets in the darkening sky, their filmy shapes slowly curling and uncurling with intense shifting colors. They are composed of tiny ice crystals more than twice as high as ordinary clouds, 9-16 miles up, in the stratosphere and form at temperatures of minus 85 Celsius and below. The crystals are all of similar size and they diffract the high altitude sunlight to make the colours." "Search for nacreous clouds at high latitudes (e.g., Scotland, Scandinavia, Iceland, Northern US) in winter and preferably downwind of mountains," Cowley advises. "They like stormy weather that perhaps creates gravity waves to loft the necessary moisture to make them upwards across the tropopause into the stratosphere. Once seen they are never forgotten!"www.spaceweather.com